A known control device for controlling the drive of a three-phase rotating machine having two three-phase winding sets includes a power converter for one unit and a power converter for another unit. Each of the power converters is associated with corresponding one of the winding sets.
For example, Patent Document 1 (JP-A-2011-152027) discloses a control device including a power converter in one unit and a power converter in another unit. Each of the power converters supplies current to corresponding one of the two winding sets of a three-phase motor. The control device performs the feedback control of the sum of the currents supplied from the two power converters to the corresponding two winding sets.
A control device may control only the sum of the currents output from the two power converters. In this case, if the two units are different in resistance, a current difference arises between the two units. The current difference is likely to cause torque ripples and worsen the heat characteristic, particularly, during low speed rotation. Also, if one of the units is accidentally opened, no current flows in the one and an excessive current equivalent to twice the normal current flows in the other which is in normal.